Blister on bottom, 18mo

[CookAMH]

My 18mo DS has a blister that is raised, not smooth, and is thin and about 1cm long on his butt cheek. He had a tiny bit of poo that I wasn't able to change right away two days ago so it was next to his skin for longer than I wanted, and his bottom was red afterward and a rash seemed to progress yesterday. I noticed the blister today, it doesn't seem to bother him. I've been using thick Weleda diaper cream on it. He wears pfs with a disposable liner. Anything else to do, maybe a soak in the tub? We have fleece liners I can start using to wick more moisture away until it heals. This is the first time he's actually had a blister!

Only change has been trying out Method free and clear detergent a week or so ago, no extra stinks or skin issues noticed.

[Qbear'smama]

Did he eat anything weird prior to the blister? I ask because when DD was a toddler she had reactions to bananas and it was like her poop after eating a banana made her bum look like she had a chemical burn, it was brutal. She seems to have outgrown it, but it happened once or twice and I think what she had sounds kinda like what you describe.

[CookAMH]

I can't really think of anything but I wondered that.

The blister was naturally burst by that afternoon (actually had two) and now they look like a sore he had while we were away from him 3 days a couple weeks ago, and the burst blister took a while to heal.